Try textPlus 4. It's finally been updated to the latest version for Canadian customers (textPlus 4 used to be US only). As far as I know, you can text any Canadian or US number, with the exception of a few carriers not being supported.
It's free (ad based) so you can give it a try, you can also pay $2.99 to remove the ads forever. It also supports MMS, which is nice.